1. Field of the Invention
The present invention relates to a process for producing a semiconductor device. More particularly, the present invention relates to a process for producing a semiconductor device which comprises, in a process comprising forming a pattern of an organic polymer resin as an organic protective film on the surface of a semiconductor element and cleaning an electric conductive layer at open portions of the pattern by the oxygen plasma treatment, adjusting the temperature of the oxygen plasma treatment at 100xc2x0 C. or higher so that formation of cracks is prevented by lowering the modulus of the organic protective layer and improving adhesion between the organic protective layer and a sealing resin.
2. Description of Related Art
Heretofore, as the protective film of the surface and the interlayer insulation film of a semiconductor element, polyimide resins having excellent heat resistance, electric properties and mechanical properties have been used. However, significant improvements in resistance to heating cycles and resistance to heat shock are required for these films as the semiconductor element is highly integrated and has a greater size, the package becomes thinner and smaller and the mounting on the surface is conducted by solder reflow. Therefore, a resin exhibiting more excellent performance is desired.
On the other hand, a technology for providing photosensitivity to a polyimide resin itself is attracting attention. For example, it is attempted that a photosensitive resin of the negative type comprising a constituting unit represented by formula [1]: 
and a photosensitive resin of the positive type comprising a polybenzoxazole precursor and a compound having a quinone diazide group (Japanese Patent Application Publication Heisei 1(1989)-46862) are used.
When an organic polymer resin is used for a semiconductor device, in general, a layer of the organic polymer resin is disposed on the outermost surface of the semiconductor device, the disposed layer is treated by the pattern working and curing so that an organic protective film which is stable mechanically and formed under heating. An inorganic protective film such as a film of silicon oxide and a film of silicon nitride which coats an electric conductive layer at open portions is removed by etching so that the electric conductive layer (a bonding putt) is exposed and the exposed electric conductive layer is cleaned by the oxygen plasma treatment. However, in the above treatments, an undesirable phenomenon frequently takes place in that cracks are formed in the organic protective film during the oxygen plasma treatment due to dust (floating dusts) from the outside contaminating the organic protective film or at corner portions of steps on the surface of the semiconductor element.
A semiconductor device is, in general, used as a package. From the standpoint of the reliability of the semiconductor device, it is required that the semiconductor exhibit excellent adhesion with a sealing resin.
The present invention has an object of providing a process for producing a semiconductor device in which, when a pattern of an organic resin disposed on a semiconductor element is used as the organic protective film and an electric conductive layer at open portions is cleaned by the oxygen plasma treatment, formation of cracks on the organic protective film can be suppressed and adhesion between the organic protective film and the sealing resin is improved.
As the result of intensive studies by the present inventors to achieve the above object, it was found that, when the oxygen plasma treatment was conducted at a temperature of 100xc2x0 C. or higher, the formation of cracks was suppressed since the modulus of the organic protective film can be reduced and the adhesion with the sealing resin could be improved. The present invention has been completed based on this knowledge.
The present invention provides:
(1) A process for producing a semiconductor device which comprises forming a layer of an organic polymer resin on a surface of a semiconductor element, treating the formed layer by pattern working and curing, etching the element using the patterned and cured layer as a mask to expose an electric conductive layer at open portions, treating the element with oxygen plasma at a temperature of 100xc2x0 C. or higher and cleaning the electric conductive layer at the open portions;
(2) A process described in (1), wherein the oxygen plasma treatment of the semiconductor element is conducted at a temperature in a range of 150 to 250xc2x0 C.;
(3) A process described in any of (1) and (2), wherein the layer of an organic polymer resin is a layer which comprises a photosensitive resin composition comprising at least one resin selected from the group consisting of polyimide precursor resins and polybenzoxazole precursor resins;
(4) A process described in (3) wherein the photosensitive resin is a photosensitive resin of a positive type comprising the polybenzoxazole precursor resin; and
(5) A process described in (4), wherein the photosensitive resin is a photosensitive resin of a positive type comprising the polybenzoxazole precursor resin and a compound having a quinone diazide group.